1. Field of Invention
This invention relates to transmissions, and more particularly adapted to a transmission device between a primary motor shaft and an output drive shaft connected to the wheels of a self-propelled lawn mower.
2. Description of Related Art
It is known in the art to use variable speed transmission assemblies on self-propelled walk-behind lawn mowers to permit the ground speed of the mower to be varied while maintaining a constant engine speed. A constant engine speed is desirable because it facilitates, for example, effective cutting by the lawnmower mower blade.
Previous variable speed transmission designs have incorporated various gear arrangements or multiple drive belt and multiple pulley systems to propel the lawn mower or tractor while still maintaining a constant engine speed. For example, some planetary gear arrangements include a series of intermeshed gears to provide a suitable mower axle speed when the engine is operating at a relatively fast engine shaft speed. Multiple drive belt and pulley systems typically include at least one belt tensioner or idle pulley which is merely used to maintain tension on the belts. The transmissions have used various clutch designs to connect the motor shaft to the output shaft of the transmission. Typical dog clutch designs require several plates in order to transmit rotation of the input shaft to the output shaft. These designs constitute pieces that are complicated to produce and of relatively high cost. Additionally, these systems generally require more space and greater number of parts, which increase the mower cost since the systems require more expensive production and assembly operations.
An improved variable speed transmission which includes a declutching mechanism that is less costly to manufacture and allows for greater ease of control by the operator is desirable.